PHP：在非对象上调用成员函数prepare（）[复制]

Question

This question already has an answer here:

• Call to a member function prepare() on a non-object error [duplicate] 2 answers

My PHP function is very simple. It's just using prepared statements to query the database, but I can't understand why it's not working.

I keep getting a 'Call to a member function prepare() on a non-object' error, even though I have declared $conn as a private variable and using $this->conn

<?php

require_once 'constants.php';

class Mysql {

    private $conn;

    function ___construct(){

        $this->conn = new mysqli (DB_SEVER, DB_USER, DB_PASSWORD, DB_NAME);
        if (!$this->conn){
            die('There was a problem connecting to the database!');
        }

    }

    function verify_name_and_pass ($un, $pwd) {

        $query = "SELECT * FROM users 
                  WHERE username = ? AND user_password = ?
                  LIMIT 1";

        if ($stmt = $this->conn->prepare($query)) {

            $stmt->bind_param('ss', $un, $pwd);
            $stmt->execute();

            if ($stmt->fetch()) {
                $stmt->close();
                return true;            
            }

        }       
    }   
}

</div>

Answer 1

The problem is your __construct() function. There is at least one typo:

• __construct() is spelled with 2 _, you spelled it with 3.
• You probably meant to use DB_SERVER instead of DB_SEVER.

Also, once you established that $this->conn is not null, you should check that the connection is correctly established by reading $this->conn->connect_errno and making sure it's 0.